This invention relates to a flight for a chain, and, more particularly, to a flight including integral means for attachment to a chain link.
This invention arose out of the need for a chain to convey pellet-like bulk material, such as kernel corn, wheat, barley, ground coffee, and so forth, where preservation of the edible quality of the material is an important concern in its handling techniques. The edible quality of the material would be damaged if contaminating lubricants were used in the conveying equipment or if there were turbulence in the grain during the conveying process, tending to break up the grains and cause dust.
Previous chains used for this purpose provide flights having wedge-shaped or inverted V-shaped cross-sections, designed to directly push the material to be moved. The flights are made of metal and are either bolted to the chain, welded to the chain or cast as an integral part of the chain links.
In conveying bulk material, it may be desirable to change the configuration or spacing of the flights to match their dynamic characteristics with the density, moisture content, and flow characteristics of various bulk materials. In the case of flights which are cast as an integral part of the chain link or which are welded to the link, it is impossible to interchange flights or to change the spacing between flights without disassembling the links. In the case of flights which are bolted onto the links, it is generally required that the links have tabs or some kind of projections onto which the flights can be bolted. This means that the spacing of flights cannot be changed without disassembling the chain unless there are many links on the chain with the necessary tabs. Chains with large numbers of tabbed links are cumbersome and expensive. The excess number of tabs would also tend to adversely affect the flow characteristics of the bulk material, as the material would catch on the exposed tabs.
Metal flights are heavy and produce a substantial amount of friction and wear when sliding on the bottom of the bin. Lubricants generally cannot be used where they would come in contact with grains or other foodstuffs, so much energy is required to overcome the friction and drive the chain.
If there is blockage in the bin putting excess force on the metal flights, it is possible to damage not only the flights but also the chain, bin, sprocket, and other parts of the system.
The use of resilient polymeric links and polymeric parts of links is known in the chain art. However, polymeric pusher flights have not been used before. U.S. Pat. No. 4,096,943 "Gentsch" and U.S. Pat. No. 3,842,968 "Owens", both of which are hereby incorporated by reference, show snap-on attachments for chain links. Both Gentsch and Owens disclose a top plate which may be snapped onto a roller chain to form a conveyor chain which carries articles on its top surface. Both top plates are made of a polymeric material and both top plates have two spaced-apart legs which may be flexed in order to be separated and to be mounted on the outside of a chain link. The Gentsch top plate has indentations in the legs to accept an extended chain pin so as to attach the top plate to the chain. The Owens attachment has legs which contact the upper and lower edges of the sidebars of the chain and the outer surface of the sidebars in order to attach the top plate to the chain.
The attachments in the Gentsch and Owens patents are not intended to withstand substantial forces tending to pull the attachment off of the chain. The attachments of Gentsch and Owens will not experience a substantial force relative to the chain during normal operation, because the vertical load of the conveyed articles is taken by rails which are part of the conveyor. These attachments were not meant to sustain the stresses which are encountered by a flight which pushes bulk material.